Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support

[Vlad Zolotarov]

On 10/07/15 11:00, Vlad Zolotarov wrote:
> On 10/07/15 09:53, Avi Kivity wrote:
> > On 10/07/2015 12:58 AM, Stephen Hemminger wrote:
> > > Go ahead and submit a seperate taint bit for UIO as a patch.
> >
> > Taint should only be applied if bus mastering is enabled (to avoid 
> > annoying the users of the original uio use case)
>
> Pls., note that this series would enable the legacy INT#X mode if 
> possible 

By default I meant.

> and this, of course, without enabling bus mastering and without 
> tainting the kernel.
> This means that the current users of uio_pci_generic won't feel/get 
> any difference after/if these patches are applied since before these 
> patches it could only be used with the devices that do have INT#X 
> capability.
>
> > > On Tue, Oct 6, 2015 at 10:41 PM, Alex Williamson 
> > > <alex.williamson@xxxxxxxxxx <mailto:alex.williamson@xxxxxxxxxx>> wrote:
> > >
> > >     On Tue, 2015-10-06 at 22:32 +0100, Stephen Hemminger wrote:
> > >     > On Tue, 06 Oct 2015 12:51:20 -0600
> > >     > Alex Williamson <alex.williamson@xxxxxxxxxx
> > >     <mailto:alex.williamson@xxxxxxxxxx>> wrote:
> > >     >
> > >     > > Of course this is entirely unsafe and this no-iommu driver
> > >     should taint
> > >     > > the kernel, but it at least standardizes on one userspace API
> > >     and you're
> > >     > > already doing completely unsafe things with uio.  vfio 
> > > should be
> > >     > > enlightened at least to the point that it allows only
> > >     privileged users
> > >     > > access to devices under such a (lack of) iommu
> > >     >
> > >     > I agree with the design, but not with the taint argument.
> > >     > (Unless you want to taint any and all use of UIO drivers which 
> > > can
> > >     >  already do this).
> > >
> > >     Yes, actually, if the bus master bit gets enabled all bets are
> > >     off.  I
> > >     don't see how that leaves a supportable kernel, so we might as well
> > >     taint it.  Isn't this exactly why we taint for proprietary
> > >     drivers, we
> > >     have no idea what it has mucked with in kernel space. This just 
> > > moves
> > >     the proprietary driver out to userspace without an iommu to
> > >     protect the
> > >     host.  Thanks,
> > >
> > >     Alex

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